Expanding stone baskets for removing stones from the human urinary tract are well known. In a conventional stone basket, a helical basket is located at the forward end of a basket tube. A control wire extends through the basket tube and is connected to the forward end of the basket. A sheath is telescopically disposed over the basket tube to facilitate introduction of the instrument into the patient's urinary tract. When the sheath is in its forwardmost position, the basket is concealed within the forward end of the sheath. When the sheath is retracted to expose the basket member, the wires of the basket expand outward. Tension can be exerted on the control wire to draw the forward end of the basket rearward, causing the basket to expand radially outward even further.
The stone basket is inserted through the urethra and advanced through the urinary tract to a location proximate to the stone. The physician then retracts the sheath to expose the stone basket and then exerts a tension on the control wire to expand the basket member. The stone basket is then maneuvered under ultrasound or other suitable visualization until the basket surrounds the stone. The physician then releases the tension on the control wire and then advances the sheath to close the basket member around the stone. When the stone has been captured within the basket, the basket can be closed tightly around the stone to crush it or to grasp it as it is withdrawn from the patient.
To enable the physician to manipulate the stone basket, conventional baskets provide a handle at the distal end of the device. A pair of slides is mounted to the handle. One of the slides is connected to the sheath, and the other slide is connected to the control wire. The physician moves the first slide to retract the sheath and expose the basket. He then moves the second slide to exert a tension on the control wire to expand the basket.
There are various problems associated with conventional expanding stone baskets. One problem is that, to open the basket fully, the physician must actuate two separate slides: the first slide to retract the sheath, and the second slide to retract the control wire. When the physician's attention is focused on an ultrasound monitor to manipulate the basket to capture the stone, having to look down at the handle to locate the appropriate slide is an unwelcome distraction. Thus there is a need for a stone basket which does not require the physician to relocate his finger from one slide to another to expand and to manipulate the basket.
Another problem relates to the fact that the wires comprising the control wire and the basket member must of necessity be of small diameter to provide a basket which will collapse to a minimum diameter, thereby to minimize trauma as the basket is inserted into the patient. Minimizing the diameter of the control wire has an adverse effect on the strength of the wire, such that the control wire cannot withstand excess tension. If the physician exerts a tension on the control wire while the basket is still encased within its sheath, the basket will be prevented from expanding. The likely result is that the control wire will break, thereby rendering the basket inoperative. Thus there is a need for a stone basket in which tension cannot be exerted on the control wire while the basket is still encased within its sheath.